List of AR platform cartridges

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The AR platform has become widely popular for various applications, including simple fun, target shooting, hunting, and much more. The names "AR-10" and "AR-15" are actually trademarks of ArmaLite and Colt respectively, but the terms have become essentially ubiquitous in describing any rifle that is based on those platforms. The AR-15 rifle usually comes chambered for either the .223 Remington, or the military's higher-pressure 5.56x45mm NATO, which can safely fire the .223 Remington, while the reverse is highly advised against for safety reasons, due to the possibility of damaging the rifle, or even possible catastrophic failure that will result in injury for the shooter. The AR-15 and AR-10 can also be converted to many other calibers as well, and here we will attempt to create and maintain a definitive list of them all, if possible.

AR-15 Cartridges

Rimfire Cartridges

Centerfire Cartridges (Imperial)

Centerfire Cartridges (Metric)

Cartridges that won't feed but which are used in rifles where the receiver functions as a trigger group

(This information needs validation)

AR-10 Cartridges

Other AR pattern rifles

Some companies have created AR pattern rifles that depart from the standard AR-15 and AR-10 dimensions in order to accommodate other types of ammunition that would not fit into the those standards.

Examples include (sorted by overall cartridge length):

Cartridge Overall length
7.5×55mm Swiss 3.059 in (77.70 mm)
6.5×55mm Swedish 3.150 in (80.00 mm)
.25-06 Remington 3.252 in (82.60 mm)
7mm Remington Magnum 3.307 in (84.00 mm)
.270 Winchester 3.339 in (84.80 mm)
.300 Winchester Magnum 3.346 in (85.00 mm)
.30-06 Springfield 3.346 in (85.00 mm)
.26 Nosler 3.346 in (85.00 mm)
.28 Nosler 3.346 in (85.00 mm)
.30 nosler 3.346 in (85.00 mm)
.33 Nosler 3.346 in (85.00 mm)
.338 Lapua Magnum 3.681 in (93.50 mm)

AR Style Shotguns

A variety of manufacturers have introduced semi-automatic shotguns whose overall designs are either heavily influenced by the AR pattern rifle, or are directly based on them.

Parent Cases for Non-Standard AR Calibers

Some of the calibers listed above use a proprietary case that is specific to that given cartridge. Other cartridges were derived from re-forming an existing case and possibly trimming the length in order to arrive at a case-shape that meets the standardized SAAMI-spec dimensions.

AR-15 Parent Cases

  • .22 Nosler - (a proprietary round), uses the head and rim dimensions of the 5.56x45, along with a case-body that is similar to that of the 6.8 Remington SPC. In order to increase powder capacity, the shoulder is higher than the 6.8, and the case is also longer. The neck is sized for .224 caliber bullets.
  • .224 Valkyrie - Uses 6.8 SPC cases, trimmed shorter, and shoulder re-formed lower due to being designed for using relatively long high ballistic coefficient bullets. Neck is sized for .224 caliber bullets.
  • .25-45 Sharps - Uses standard military 5.56x45 case (also .223 cases). The neck is simply expanded to .257 caliber.
  • 6.5mm Grendel - The Grendel uses the same head and rim from the .220 Russian and the 7.62x39 with a rim diameter of 0.441-0.449. The 6.5 Grendel bullets have a true diameter of 6.71mm / 0.264" and the case can be formed from abundant 7.62x39 cases with a neck re-sizing die, as well as fire-forming a slight change to the shoulder if using a brass casing. Many popular 7.62x39 cases are made from steel, which will not work properly for reforming the case's shoulder.
  • .277 Wolverine - Standard military 5.56x45 case (also .223), shoulder is reformed lower, length is trimmed, neck is sized to accept .277 projectiles.
  • 6.8 Remington SPC- A proprietary cartridge. Developed as an all new cartridge in the hopes of gaining a military contract. Rim diameter is 0.421 inches.
  • .300 AAC Blackout - Uses military 5.56x45 (also .223). The shoulder is reformed, length trimmed, neck sized to .308 caliber. This cartridge has become very popular, and examples are available in a wide variety of styles. Bullet weights can currently be found between 100gr to 220gr, the latter of which is primarily used with a suppressor, resulting in a very quiet report while still being hard-hitting.
  • 7.62x40 Wilson Tactical - Uses 5.56 NATO cases (also .223). Shoulder is re-formed, length is trimmed, and neck is sized to .308 caliber. This cartridge is very similar to the 300 AAC Blackout, but the shoulder is slightly higher and the case is slightly taller, which allows for more gunpowder capacity when loading the lighter/shorter high-velocity bullets.
  • .338 Spectre - Uses 10mm Magnum pistol cases with a 6.8 SPC bolt-face. A shoulder is formed, and the case is lightly trimmed to length, and the neck is sized to .338, down from 0.401". The 10mm rim is 0.424" (10.8mm) in diameter, and the SPC rim diameter is 0.422" (10.7mm). The .338 caliber bullets are available in weights between 200gr-250gr.
  • .350 Legend - Proprietary cartridge. The head and rim dimensions exactly match the military 5.56x45 case, allowing the use of the standard bolt-face of an AR-15. However, the case has an added taper and is longer than 5.56x45 cases, so these cannot be reformed from any existing case. The nominal bullet diameter is .357-inch, but SAAMI specs allow the bullet diameter variance to be .355-.357
  • .357 Auto - Wildcat cartridge. Uses 10mm magnum pistol cases with a 6.8 SPC bolt-face. The existing 357-Sig pistol is a 9mm bullet shouldered into the larger 40 S&W pistol case. The 10mm cartridge and the 40 S&W are almost identical, but the 10mm case is longer and operates at a higher pressure. This means that you can use existing 357-Sig dies to re-form the straight-wall 10mm case into a shouldered .355" (9mm), and then the neck can be sized up to accept .358 rifle bullets. This is in response to the popularity of the 300 Blackout at subsonic velocities. If the bullet velocity is capped at 1,000-Feet Per Second / FPS in order to subdue the noise of firing, then the impact can be improved by increasing the weight of the bullet. The 357 Auto can be loaded with bullets in .358-caliber, while still fitting within the AR-15 COAL of 2.260". Bullet weights are currently available between 225gr-310gr
  • .358 Yeti - Uses standard military 7.62x51 cases (also .308), length is trimmed, shoulder is reformed, neck is sized to .358". Bullet weights are currently available between 225gr-310gr
  • .375 Stalker - Standard military 7.62x51 cases (also .308), length is trimmed, shoulder is reformed, neck is expanded to .375
  • .375 SOCOM Proprietary. The case head and rim dimensions exactly match the military 7.62x51 (also .308), however, the case body is slightly wider and has more taper.
  • .400 AR - Wildcat cartridge. The parent is the 7.35x51mm Carcano rifle case. It has a rim diameter of 0.447" which allows the use of an AR-15 bolt-face from the existing 6.5-Grendel or 7.62x39. The shoulder is trimmed off at a case-length of 1.700", with a COAL of 2.250", resulting in a "straight-wall" cartridge. It can accept .401-.402 rifle bullets (240gr-310gr) from muzzle-loaders, and also .400-.401 bullets from a 10mm magnum pistol (135gr-230gr).
  • .450 Bushmaster - Uses .284 Winchester cases. Cut the length to 1.700" to form a straight-wall cartridge, from 2.170". The .284 Winchester case is very similar to the .308, however, the .284 case has a body diameter of 0.500", and the .308 case has a body diameter of 0.471". Both share an identical head/rim. The 450B is limited to 35,000-psi, which is more common in pistols, and lower than similarly-sized rifle cartridges. The 450B uses .452" diameter bullets, most often seen in the abundant 45-caliber pistol styles. The 300gr version is rated at 1900fps at the muzzle, and the 250gr at 2200fps.
  • .458 SOCOM - A proprietary cartridge. The case head and rim dimensions exactly match the military 7.62x51 (also .308), but the case body is slightly wider and has more taper.
  • .50 Beowulf - Proprietary round. The case head and rim dimensions exactly match the .44-Magnum pistol case, and all dimensions from the lower part of the case matches the 50-Action Express (50 AE), which can be described as a .44-Magnum cartridge that has had the body of the case expanded to 50-caliber while leaving the head intact. However, the 50 Beowulf case is longer than the 50AE, so the 50AE cases cannot be used as a donor.

Note on donor cases: The 7.62x51 military cartridge is known in the civilian world as the .308 cartridge. Since its dimensions are taken from the 30-06 cartridge from the 1906 US Army cartridge, the lower half of these case dimensions have been used for designing the .243 Winchester, 25-06, .270 Winchester, .280 Remington, 7mm-08, .308, .30-06, .35 Whelen, and others. Any AR-15/AR-10 cartridge cases that are derived from the 7.62x51 can also possibly be formed from the aforementioned cartridges.

AR-10 Parent Cases

The AR-10 is larger and heavier than the AR-15. It was originally designed to chamber the military 7.62x51 NATO cartridge (also .308), which has a COAL of 2.800" (71.12mm)

  • .45 Raptor, uses the standard 7.62 NATO case, cut to a length of 1.800" from 2.015", resulting in a straight-wall cartridge, neck is sized to 0.452". The resulting COAL of 2.300" is only 1.02mm longer than the maximum COAL for chambering a cartridge in the smaller AR-15, however, the 45 Raptor chamber pressure is allowed to be as high as 62,000-PSI. This means that the stronger AR-10 receiver and bolt carrier group is needed for shooting this cartridge.

Other Information


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